And here is the testcql column family I created for this example:
create column family testcql
with comparator = 'UTF8Type'
and default_validation_class = 'UTF8Type'
and key_validation_class = 'UTF8Type';

As I said, the code could run successfully, and I'm able to get the total rows for the column family testcql. However, I'm very confused with "CqlQuery<String,String,String>" declaration, I know the three <String> is for the key type, value name type and value type, but if I create a column family with multiple column name type and column value type, then, how do I declare CqlQuery?